Dynamometer testing of vehicles is known per se, and can, for example, be carried out by roller type dynamometers equipped with large rollers that support the vehicle wheels, and which are used to apply a brake torque to the drive wheels of the vehicle. Such systems, however, are not always capable of providing the desired measurement accuracy and/or measurement freedom.
Another kind of vehicle dynamometers for dynamometer testing of vehicles is disclosed in U.S. Pat. No. 4,669,318 (Ångström). This document relates to an apparatus for dynamometer testing of motor vehicles, where load absorbing means in the form of a hydrostatic pump assembly has an input shaft for engagement with a drive shaft of a vehicle to be tested. Sensor means are arranged so as to allow measuring of the torque from the vehicle drive shaft. Typically, in a vehicle having two wheel drive, each drive shaft is fixedly connected to an individual apparatus of this kind, whereby a total effective torque from the vehicle can be accurately measured.
Systems of the kind disclosed in U.S. Pat No. 4,669,318 are reliable, and are capable of accurately measuring torque in steady load situations.
It is also possible to perform more complex tests using a dynamometer testing system of the above kind, both for two-wheel drive systems, and also for four-wheel drive systems. Such more complex testing, using a system of the above kind, is disclosed in the International patent application WO2007/13154 A1 (Engstroem).
There exist, however, situations where measurement results representing a true vehicle driving situation, taking into account conditions that prevail during real life driving of the vehicle on a road, are requested, but where such measurements are not possible for economical or other reasons.